Electric sound reproducer



Dec. 15, 1931. w. s. MCCLINTOCK.JR 1,836,266

ELECTRI C SOUND REPRODUC ER Filed Dec. 26, 1929 2 Sheets-Sheet lhfZ/z'aw 37% flak/004A" I dd/1M. M W P Dec. 15, 1931. w. s. M CLINTOCKJRELECTRIC SOUND REPRODUCER Filed Dec. 26, 1929 2 Sheets-Sheet PatentedDec. 15, 1 931 UNITED STATES PATENT OFFICE WILLIAM S. MCCLINTOO'K, JR,OF CHICAGO, ILLINOIS, ASSIGNOR TO THE m ml- IPANY, OF CHICAGO, ILLINOIS,A CORPORATION OF. ILLINOIS ELECTRIC SOUND REPRODUCEB Application filedDecember 26, 1929. Serial No. 416,317.

My invention relates to electric sound reproducers of the condenser orcapacity speaker ty e.

Its chief object is to eliminate the necessity of operating the capacityspeaker under a maintained high potential, while still retainingsatisfactory performance.

As a practical advantage, my invention permits operation of the capacityreproducer without use of a high voltage. or example,

I may use only two or three dry cells. I may eliminate the moreexpensive and complicated high voltage batteries or rectifier andamplifier circuits.

While by no means restricted to such use, my invention is here shown asembodied in a one way oflice telephone system. In this system is a smalltransmitter including an operating switchto be placed in one room and acapacity speaker in the other, with a transformer and two or three drycells located wherever convenient. This system as illustrated requiresno additional source of potential and no amplification.

For the effective operation of capacity speakers it has heretofore beennecessary to maintain an impressed basic high voltage of some 400 or 500volts durin o eration. This has usually been accomplis e by a B batteryor a filter circuit in the secondary or speaker circuit. Unless operatedinsuch a high voltage range, the operating characteristics'of thespeaker have been too feeble to be practicable.

In my invention I avoid the necessity of operating under any maintainedor impressed voltage on the speaker circuit. A Instead I condition thespeaker for effective operation with impulses of ordinary strength, byshocking the speaker, which is preferably accomplished by momentaryshort circuiting of the primary. I prefer to use a circuit closingswitch for the primary circuit which afl'ords an automatic, preliminary,momentary short circuiting or shunting of the primary around thetransmitter.

Another feature of m invention is that this shocking of the spea erwiththe closing of the 0 rating circuit gives a distinctive I audible signalserving as a preliminary warning that a message is about to be given..Con-

versely, the operatin switch can be arranged to give a similar shoc units release, which provides a signal that t e message has beencompleted.

Other objects, features and advantages of my invention are set forth inthe following specification and in the accompanying drawings, wherein:

Fig. 1 is a circuit diagram of a one way ofiice telephone systemembodying my invention;

.Fig. 2 is a schematic view of the transmitter, transformer and battery,and capacity speaker units of the circuit of Fig. 1,;

Fig. 3 is an enlarged plan view, with portions broken away, of thecapacity reproduoer element;

Fig. 4 is a detailed section taken on the line 4-4 of Fig. 3 showin' theattachment of-one of the lead-in wires, the dielectric and tinfoil beinomitted.

Fig. 5 is a similar detail section taken on line 55 of Fig. 3 showingthe attachment of the other lead-in wire; and

Fig. dis a detail section taken on the line 6-6 of Fig. 3 showing themounting of the condenser in its frame.

The oflice telephone system schematically shown in Figs. 1 and 2comprises in neral a transmitter 10, a transformer and ttery housed inthe case 41, and a capacity reproducer, which may be of the type shownin Kyle Patent 1,644,387. The details of the reproducer shown in detailin Figs. 3 to 6 inclusive include some variations in construction.

An operating switch conveniently housed in the handle of the transmitterand controlled by a thumb button is so arranged that immediatelypreliminary to closing the primary circuit through the transmitter, itshunts the circuit across the transmitter, thereby short-circuiting theprimary and subjecting the secondary or speaker circuit toa momentaryock.

To describe the system in Referring to Figs. 1 and 2, 11. usual type oftransmitter is provided with an electric circuit including conductors 11and 12. The conductor 11 communicates with ablade 18 of greater detail apush button switch consisting of blades 13, 14 and 15 which yield whenthe button 16 is pushed down. An insulating block 17 spaces the blades13 and 15. The conductor 12 leads to a contact 18 which is engaged byblade 15 when it is sufficiently depressed. A contact 19 on the blade 14will be engaged by the blade 13 prior to the engagement of the blade 15with the contact 18, so that the blade 14 is forced out of engagementwith the contact 21 prior to the engagement of the blade 15 with thecontact 18.

The conductorll and the blade 13 are connected with a conductor 22 whichcommunicates with the primary winding of the transformer 24. Theconductor 25 carrying the contact 21 is connected to a battery 26inpractice preferably two or three dry cells which is connected with theopposite end of the primary winding 23 by a conductor 27. The switchblade 15 is connected to the conductor 25 by a conductor 28.

The secondary 29 of the transformer is connected by conductors 31 and 32with the opposite plates 33 and 34 respectively of the reproducer 35. Ifdesired, a spark gap 36 may be used to protect the reproducer fromexcessive voltages.

The switch mechanism may be incorporated in the handle portion 40 of thetransmitter. The transformer and battery may be housed in a cabinet 41having the conduct0rs22 and 25 connected to binding posts 43 and 44. Theconductors 31 and 32 leading to the secondary 29 of the transformer aresecured by binding posts 45 and 46 respectively.

The reproducer 35 consists preferably of a metal plate 34 perforated asat 48 and is corrugated as shown in Figs. 4 and5. A thin sheet ofresilient rubber 49 is stretched over the plate 34 and its edges arewrapped around a cord 52 which is pressed into a marginal recess in theframe 51 to hold the rubber taut. The metal plate 34 is preferablyslightly convexed to maintain a fairly uniform pressure of the rubbersheet against the perforated plate. The plate 34 of thecondenser-reproducer is relatively rigid. To

provide suflicient relative flexibility of the plates, the upper plate33 is formed of tinfoil or the like which is secured to the rubber sheetby a suitable adhesive.

The tinfoil plate 33, which forms the diaphragm of the reproducer, movesupon chargmg d discharging of the condenser in proportion to thefrequency and strength of the sound waves transmitted. The plate 34 isreferably' secured to the frame portion 51 by nails 53 passing throughperforations around the edge thereof. A protecting moulding strip. 54may be fixed by screws 55 on the frame over the edges of plate 34 asshown in Fig. 6.

The conductor 32 is electrically connected to the plate 33 by a bindingpost consistingof a bolt 56 passing throu h an over-size opening in theplate 34 and t rough washers 57 and 58 which engage the plate 32.

The conductor 31 is electrically connected with the plate 34 by alead-in strip nailed between the frame and an edge of the plate (Fig.4). i

If desired, a decorated paper cover or picture 61 may protect thedelicate tinfoil plate 33 as indicated in Fig. 2. The reproducer may behung by an eye 62 as shown, or may stand on a base.

In the normal operation of my system, the operator lifts the transmitterto his mouth by the handle'40, pressing the buttom 16. This initiallyengages the blade 13 with the contact 19 of the blade 14, thereby shortcircuiting the battery 26 through the primary 23 of the transformer, andgives the condenser-reproducer 35 a momentary shock. The shocking of thecondenser-reproducer has the dual function of conditioning thereproducer and giving an audible signal that a message is to be given.The switch in the transmitter handle next disengages the blade 14 fromthe contact 21, breaking the momentary short circuit. Immediatelythereafter the blade 15 engages the contact 18, placing the battery inseries with the transmitter and the primary, which constitutes thenormal speaking circuit.

For a two way or inter-communicating installation another system can beused with the reproducer of one and the transmitter of the other at therespective terminals. In such a system of course the person addressedcan talk in reply, and also the party addressed, by merely pressing thebutton on his transmitter, can indicate to the other party that he isready to receive the message without using the conventional Hello.

The conditioning of the capacity speaker by such a momentary shock isnot permanent, but from my experiments it seems to last at least for afew hours. However, the automatic shocking of the reproducer prior toeach communication always insures that the capacity reproducer isproperly conditioned for operation. Such a conditioning of thereproducer is somewhat analogous to a molecular polarization of therubber, even though it is of course a non-metallic substance. Thisanalogy is further borne out by the cumulative effect of such shocking.With each additional shocking the effect becomes more lasting.

I believe from experiments I have conducted that the advantages ofrelying upon shocking of the reproducer to condition it for effectiveoperation, instead of maintaining an impressed high voltage, is not onlyin eliminating the necessity for more elaborate means for maintaing suchhigh voltage, but also that, in operating the capacity reproduc'er on abasic voltage of zero, a more favorable operating range results withgreater sound wave producing power from the reproducer in proportion tothe charge power.

While my invention has been described as adapted specifically to anofiice telephone system and with one specific circuit illustrated, Icontemplate that many other embodiments of my invention may be made in aradio re ceiving set without departing from the scope or spirit of myinvention as set forth in the appended claims.

I claim:

1. The combination with a condenser-reproducer of means for momentarilyabnormally electrically shockin the condenserreproducer to condition itor normal operation.

- 2. The combination with a condenser-reproducer and a receiving circuittherefor operating upon a basic voltage of zero, of means for abnormallyelectrically shocking the con- 'closable operating circuit therefor,which consists in subjecting the reproducer to a momentary electricalshocking preliminary to closing the circuit for normal operation.

5. A method of operating a condenser reproducer comprising condenserplates with a pliable resilient dielectric there-between, which consistsin normally operating the circuit of the reproducer without a high basicvoltage and from time to time subjecting the reproducer to an abnormdlelectrical conditioning.

6. The combination of a condenser-reproducer comprising a pair ofcondenser plates and a rubber dielectric there-between, a secondarycircuit for the reproducer, a primary coupled with the secondary, meansfor electrically impressing sound waves thereon, and means formomentarily subjecting the rimary to an abnormalcurrent for shockmg thecondenser-reproducer to condition it for normal operation in the absenceof an impressed high voltage.

7. In a device ofthe class described, tramsmitter means for convertingsound waves into electrical waves, means comprising a densenreprfoducerfor converting the ctric'al waves into sound waves, and means forproducing an electrical shock in said re producer. 7

8. In a device of the class described, a transmitter, acondenser-reproducer therefor, a source of potential, normal operatingcircuits connecting the several parts of the device, and circuit closingmeans therefor,- causing said potential source to shock said reproducer.v

9. In a device of the class described, a transmitter, acondenser-reproducer, an electric circuit connecting said transmitterand reproducer, a source of electrical potential for said transmitter,circuit closing means for connecting said source in series with saidtransformer and comprising a portion adapt ed to momentarily shunt saidtransmitter prior to connecting it in series whereby a shock istransmitted to said reproducer.

10. In a device of the class described, a transmitter, acondenser-reproducer, an electric circuit connecting said transmitterand said reproducer, a source of electrical potential for said circuit,a potential transformer in the circuit between the transmitter and thereproducer, circuit closing means for connecting said source in serieswith said transmitter and the primary of said transformer, and means formomentarily short circuiting said source through the primary of saidtransformer.

11. The combination with a condenser reproducer of a normal operatingcircuit therefor, a switch for said circuit, and means actuated uponoperation of the switch for first momentarily shocking the circuit forconditionin the condenser-reproducer.

12. n a device of the class described, a transmitter, acondenser-reproducer, an electric circuit connecting said transmitterand said reproducer, a source of electrical otential for said circuit, apotential trans ormer in the circuit between the transmitter and thereproducer, circuit closing means for connecting said source in serieswith said transmitter and the primary of said transformer, including aportion adapted to momentarily short circuit said source through theprimary of said transformer upon actuation of said circuit closingmeans. v

13. In an acoustic device of the class described, a transmitter, acondenser-repro ducer, a reproducer charger in electrical series withsaid reproducer, a source of potential for said transmitter, circuitclosing means for connecting said source in series with said transmitterand said charger, and means adapted to short circuit the source throughthe charger.

14. In an acoustic device of the class de scribed, a transmitter, acondenser-reproducer, a reproducer charger in electrical series withsaid reproducer, a source of potential for said transmitter, switchmeans for connecting and disconnecting said source in series with saidtransmitter and said charger, including a portion adapted to shortcircuit the source through the charger upon actuation of said switch.

15. A telephone system of the class described comprising a transmitter,a low voltage battery, a transformer, a circuit for the three, a switchfor the circuit,-and a secondary circuit through the transformer, acondenser-reproducer in the secondary, and means for short circuitingthe battery through the primary of the transformer for shocking thecondenser-reproducer.

In witness whereof, I hereunto subscribe my name this 24th day ofDecember,1929. W'ILLIAM S. M CLINTOCK, J R.

